with RX is buying oxycontin online legal?

with a prescription from a doctor, is it legal to get oxycontin online? i am prescribed to Oxycontin 40mg, and also instant release oxy 15's. Can someone give me a website that i can buy 40s from? im trying to find the name brand oxycontin for as cheap as possible. i have insurance, but ever since they came out with a generic oxycontin 40, the copay on the namebrand is almost full price without insurance. please let me know. a website or any info would be great.
thanks!